The present invention relates to a device for sharpening rotating blades.
The device in question can be used for sharpening any type of rotating blades, both of the disc type and of the so-called "hook blade" type having blades projecting radially from a rotating hub.
The present invention finds particularly advantageous application in the field of filter cigarette making machines in that such machines utilize rotating blades both for cutting the rods of cigarette and for cutting the filters.
In cigarette making machines, and in particular in filter fitting machines, to which the following description will make exclusive reference without any loss of generality thereby, it is known to utilize rotating blades constituted by disc knives the outer periphery of which is normally able to rotate within the space lying between two grindstones keyed onto a shaft forming a predetermined angle with the axis of the associated knife. For the purpose of compensating the reduction in the radius of the said knife due to wear, the shaft supporting the grindstone is normally mounted on a slide movable in a direction transverse the shaft itself under the action of a transmission manually actuated by an operator, or else incrementally by a motor.
In the case in which the position of the said slide is controlled manually, the relationship between the periphery of the knife and the associated grindstone is not always correct and this gives rise either to a perfect sharpening obtained with an excessive removal of material or else to an insufficient sharpening. This latter disadvantage is normally obviated by incremental motorised control in that it is normal to adjust the drive motor in such a way that the removal of material is always in excess. In this way, however, wear on the knife is always more rapid than necessary.